This is a detailed study into the internal aerodynamics of labyrinth seals, with pmic| reference to the effects of abradable honeycomb stators on labyrinth seal leakage.- A extensive experimental programme established tables of friction factor for three different grades of honeycomb used by industry, and examined the effect of both Reynolds number and clearance on these friction factors. The friction factor associated with a aerodynamically smooth surface was also experimentally determined in order to establish the experimental method. The experimental data was used to model the different grades of honeycomb used as stator material in numerical simulations of a number labyrinth seals, and allowed for comparison of the leakage associated with both smooth and abradable stator straight through labyrinth seals. Step-up and step-down seal geometries were also considered, and the effects of pressure ratio, clearance and rotation on labyrinth seal leakage was examined on all modelled seal types. This numerically generated leakage data was comprehensive enough to allow for the creation of a second-generation one-dimensional labyrinth seal leakage predictor tool of the type used by design engineers in network models. This tool accounts for stator material, seal clearance, overall pressure ratio, rotation and seal geometry, and the accuracy associated with this tool allows labyrinth seal leakage to b predicted to within 10%. Functions of discharge coefficient and carry-over factor obtained from the numerical predictions are used by this tool, and as such it is capable of dealing with a large number of different operating conditions for all the seal types modelled.

No description available.

Gas turbines provide an efficient source of power for aviation and electricity generation and future demand is set to increase. Efforts to further improve efficiencies have led to the integration of thermal barrier coatings (TBCs) in advanced turbines. In order to maximise the efficiency gains offered by the coatings, accurate lifing models must be developed based on reliable measurements of the operating conditions and supported by quantitative non-destructive evaluation (NDE) of coating degradation in service. Although a range of NDE techniques have been studied for this application, the nature of the coatings present particular practical challenges. A novel approach, introduces rare-earth dopants into the TBC ceramic to make the material luminescent. This approach has several technical advantages including the capability for in-situ measurement and assessment of damage before it becomes critical. The present study investigates the use of luminescence for NDE of TBCs through two applications, erosion detection and thermal history measurement. The former detects partial failure of the ceramic coating while the latter records the thermal exposure of the coating material which is related to the primary failure mode of TBCs. The addition of different dopants in layers can be used to determine the remaining coating thickness. The first quantitative study of this approach, conducted in this project, has demonstrated, through two methods of image processing, that multi-layered doped coatings provide a detailed, precise and accurate profile of the erosion damage. An estimated precision of ±5μm was achieved while the accuracy of the depth profile was comparable to alternative, sophisticated thickness profiling techniques. Furthermore, the addition of dopants did not alter the failure mechanisms compared to standard TBC architectures and coatings have exhibited no damage after operation on a turbine blade in a Rolls-Royce Viper jet engine. The luminescence is affected by the microstructure of the host material which can be used to record the extent of the thermal exposure of the coating. A greater understanding of the link between the microstructural and luminescence properties was achieved by comparing luminescence measurements to results from standard materials characterisation techniques. Powder samples were synthesized by the sol-gel route to provide the first evidence of a link between the phosphorescent decay time and the crystallite size, explained by energy transfer to quenching sites at the edges of crystallites. YAG:Eu coating samples were produced using the same method as for TBCs. Heat treatment of the coatings instigated crystallisation which caused changes to the emission spectrum and an increase in the decay time, enabling temperature measurements between 300 and 880°C. A similar coating was applied and successfully tested in an engine test bed and measurements of the phosphorescence indicated the thermal profile during operation. When embedded in a TBC, the changes in the phosphorescence of the YAG:Eu altered such that temperature measurement range extends to at least 1150°C, covering the typical operating range of TBCs. This suggested that the mixed material is a favourable candidate for thermal history measurements in TBCs.

The need to meet ever more stringent emission regulations and the desire to improve fuel economy has led to the significant development of the gasoline spark ignition combustion engine in recent years. One area of development has been mixture preparation, and PH (Port Fuel Injection) has been introduced to increase engine responsiveness whilst meeting emission regulations. Successful PH designs however depend upon good targeting of the fuel spray onto the back of the intake valve. Geometric predictions based on injector axis and spray bone angles have been used in the past, but require development to account for the momentum exchange between the spray and the charge air. Alternatively CFD (Computational Fluid Dynamics) can be used. In this study a validated methodology has been successfully developed using the commercial CFD code Fluent5.5, to simulate the spray behaviour from a multi-hole port fuel injector. The approach taken ignored the primary and secondary atomisation phases, and instead droplets were injected at the injector tip position. The droplets velocity and size were then tuned until the predicted spray profile matched the measurement data at 60rnm and 90mm downstream of the injector tip. Having developed a tuned injector model, CFD simulations assessing the injector targeting performance of the Jaguar AJV8 engine were then undertaken. Based upon these assessments some suggestions to improve the engine's injector targeting performance were made. Before this methodology could be developed, a series' of experiments were necessary to characterise a state of the art port fuel injector. A combination of Planar Mie and PDA laser techniques, were used to measure how the spray behaved under different operating and atmospheric conditions. As well as providing spray boundary and validation data, an in depth understanding of the spray structure was gained for both pulsed and continuous injector operations.

The intense global competition in the commercial aviation and power generation industry is placing a significant pressure on minimizing cost while meeting challenging goals in-terms of performance, efficiency, emissions and reliability. During recent years an opportunity has been identified and is currently being focused on, for reducing the design and development cost by largely replacing the larger scale and expensive hardware based testing, with multi-fidelity and cross-domain predictive simulation platforms. A greater use of such predictive simulations not only save some costs directly associated with hardware design and testing but also enables engine design trade-offs and component interactions, to be studied in detail earlier on before a commitment is made towards the final hardware design. Experts have estimated a reduction of 30 to 40% in development time and cost when such dynamic simulation techniques are implemented. Furthermore, to keep the engine development on going, joining forces with various gas turbine industrial manufacturers, research centres and universities especially within the European Union is of utmost importance because tomorrow's advanced engine configurations can no longer be developed with today's simulation tools in the way they are currently used. The research work, presented within this thesis has been conducted under the flagship of "VIVACE-ECP" (Value Improvement through a Virtual Aeronautical Collaborative Enterprise - European Cycle Program) an European Union sponsored collaborative research project, geared towards the development of an advanced gas turbine performance modeling and simulation platform with cross domain analysis capability. The research work undertaken by the author within the scope of this thesis and the project, fundamentally encompasses around the two distinct aspects; 1) development of a new and modern (0-0) gas turbine performance simulation industrial core tool called as PROOSIS and 2) development in the form of a prototype demonstrator a multi-fidelity simulation technology, fundamentally aiming to reduce engine development cost and time. The new and modern PROOSIS application framework conforms to an 00 programming schema giving the tool features in terms of flexibility, extensibility, robustance, etc. Although, PROOSIS has been envisaged as a long term development process, several of its current capabilities and component modelling philosophies have been discussed in detail. The prototype (3-D) integrated Aerodynamic Component Zooming Framework makes the optimal use of two different simulation platforms at different fidelity levels, thus allowing for variable' complexity analysis to be performed as required. In order to demonstrate the prototype (3-D) integrated Aerodynamic Component Zooming Framework a case-study has been developed. The case study is to study the effect of VSV on a single stage compressor (or fan) during part speed performance and which was successfully completed. The integrated component zooming technique has been performed using a custom developed workflow management tool referred to as "Integrated Workflow Controller" making use of a distributed computing architecture. The key contribution of the author within the scope the project and the thesis has been the development of the modern object oriented GT (0-0) cycle code PROOSIS framework and the development of the modern (3-D) integrated aerodynamic compressor zooming framework. Within this thesis, full and comprehensive information on the research work undertaken by the author in order to achieve the above discussed goals, along with suitable results have been presented. Also discussed in detail are results generated as a part of the software testing, verification and validation of both 1) PROOSIS and 2) (3-D) Integrated Aerodynamic Component Zooming Framework. In an effort to reduce engine development cost and time as discussed earlier, the research work undertaken by the author part of the CU team has made an extensive and optimal use of modern, sophisticated and cross domain, numerical simulation technology readily available and affordable, at different fidelity levels. Additionally, the collaborative effort which has been another key aspect of the project in creating a standard and a modem GT simulation framework (with a prototype component zooming capability) for the advanced gas turbine systems in future has also been achieved. This has been possible by mutually sharing the technical expertise between all participating GT industrial manufacturers, research centres and universities within the European Union. It is the author's opinion that both of the above highlighted developments form a strong foundation for future technological developments leading to an even more sophisticated and capable, multi-disciplinary and multi-fidelity simulation environment which will lead to a significant reduction in engine development cost and time.

The high temporal resolution of Acoustic Emission offers great promise in the on-line monitoring of complex machines such as diesel engines. The fuel injection process is one of the most important processes in the diesel engine and its timing and fuel delivery control are critical in combustion efficiency. In this work, the phenomena leading to the generation of acoustic emission during injection are investigated by simulation of the injection process in a specially designed rig and through test in running engines on a test-bed. Signal processing approaches are devised to produce diagnostic indicators for the quality of the injection process. The novelty of the research lies in; 1) obtaining a coherent set of data which allows the separation of the part of the signal associated with injection in a given cylinder from other sources adjacent in time and space, and 2) in developing a signal processing approach which allows this separation to be achieved on line using an array of sensors. As such, the research is generic to multi-source multi-sensor analysis in machines. A series of experiments were performed on an experimental injector rig, and two-stroke and four-stroke diesel engines under different operating conditions. The injector rig experiments provided useful information on the characteristic signatures of the injection events, finding which could be implemented to the more complex signal from the running engines. A number of sensor arrays (sets of two and three sensors) were used on two types of four-stroke engine at different running speeds to investigate the source identification of the injection events, the essential strategy being to add complexity to the information in the AE record by using engines of varying degrees of mechanical sophistication. It has been concluded that the AE signals are generated by the mechanical movements of the components in the pump and injector as well as aspects of the fuel flow through the injector and the piping. Also, it is found that the temporal structure of the AE is highly sensitive to sensor position, and that transmission path differences to a sensor array are generally large enough to allow source separation. Applying a purpose-designed thresholding technique, followed by canonical correlation allows the separate identification of parts of the AE signal in the short crank angle widow where sources involved in injection, inlet valve opening and combustion are operating.

Gas turbines are comprised of many parts, which are often expensive and required to survive a harsh environment for significant periods (with or without reconditioning). To differentiate between parts, and facilitate keeping accurate historical records, they are often given a unique identification number. However, manually recording and tracking these is difficult. This has led to increased adoption of machine readable codes to help reduce or eliminate many of the issues currently faced (mostly human error). The harsh environment of a gas turbine means that typical methods of applying machine readable codes, such as printed adhesive labels, are simply not durable enough. Direct part marking (DPM) is necessary to ensure the desired longevity of the code over the part's useful life. The research presented in this thesis was approached in two main phases. Firstly, the author sought to investigate the technical solutions available for the elements required of a part tracking system (encoding, marking and scanning). This included identifying the characteristics of each and their compatibility with one other (across elements). In conjunction with Alstom, criteria were identified that were used as a basis for comparison so that the preferred technical solutions could be determined. The outcome of this process was enhanced by the author developing a number of industrial contacts experienced in implementing part tracking systems. The second phase related to the legibility of the codes. The harsh environment of a gas turbine results in surface degradation that may in turn reduce the legibility of any machine readable codes present. To better understand why read failures occur, the author _rst looked to the scanning process. Data Matrix symbols (marked via dot peen) require the scanner to capture an image for processing. Image capture is typically achieved using a charge-coupled device (CCD), each pixel of which induces a charge proportional to the incident illumination. This illumination is received via reflection from the surface of the part and hence the Data Matrix marked on it. Several surface features were identified that govern the way in which the part surface will reflect light back to the scanner: surface roughness, dot geometry and surface colour. These parameters are important because they link the degradation mechanisms occurring { broadly categorised as deposition, erosion or corrosion { with the scanning process. Whilst the degradation mechanisms are distinctly different in their behaviour, their effect on surface reflectivity is common in that they can all be characterised via the surface parameters identified. This was deduced theoretically and so the author completed tests (utilising shot blasting to change the surface roughness and oxidation to change its colour, independently) to show that these surface parameters do indeed change with the introduction of surface degradation and that there is a commensurate change in symbol legibility. Based on the learning derived with respect to Data Matrix legibility, the author has proposed a framework for developing a tool referred to as a Risk Matrix System. This tool is intended to enhance the application of part tracking to gas turbine engines by enabling symbol durability to be assessed based on the expected operating conditions. The research presented is the first step in fully understanding the issues that affect the legibility of symbols applied to gas turbine parts. The author's main contribution to learning has been the identification of knowledge from various other sources applicable to this situation and to present it in a coherent and complete manner. From this foundation, others will be able to pursue relevant issues further; the author has made a number of recommendations to this effect.

The development of aero-gas turbines is moving towards more efficient engines with higher pressure ratios and increased Turbine Entry Temperatures. This leads to increases in overall turbine blades temperatures which has resulted in the widescale development of turbine blades with film cooling and Thermal Barrier Coatings (TBCs) which reduce the metal temperature of the blade. The air used for film cooling is directed around the blade by internal passages within the blade, current engines are experiencing hot corrosion in areas of these internal passages, even with internal aluminide coatings. The trend for more efficient engines means that corrosion of the internal passages will become more common, coupled with the inability to inspect the internal passages of turbine blades in service, results in a requirement for an improved coating for the internal passages of turbine blades. The aim of this study was to develop a coating which provides improved corrosion and oxidation performance over a standard vapour aluminide on single crystal CMSX-4 turbine blades material. The coating needs to be compatible with the Rolls- Royce bond coat and the Rolls-Royce manufacturing strategy. The study investigated a number of additions which could be used to improve the performance of an aluminide coating. Silicon was selected as the optimum addition on the basis of performance and ease of deposition. The work then assessed the influence of various production parameters on the formation of a silicon-aluminide coating. It was possible to control the level of silicon deposited in the coating. Performance testing, using cyclic oxidation and salt recoat hot corrosion tests, of various silicon aluminides developed in this programme demonstrated at least a doubling in life compared with vapour aluminide coatings.

The author was responsible for the Guarantee verification, testing and eventually Acceptance of all of National Power's Combined Cycle Gas Turbines for its commercial operation. It was discovered during the early Acceptance Testing of these power stations that the Original Equipment Manufacturers (OEMs) used empirical and indirect methods to derive the gas turbine inlet temperature. This had direct impact on the life of the gas turbine components and revenue earned in terms of increase in maintenance costs and loss in generating power. It became absolutely imperative that alternative methods should be quickly deployed on National Power's gas turbines to substantiate or otherwise the already used indirect methods of running the gas turbines. A completely novel method of using ceramic thermocouples probes and embedded ceramics onto blades to monitor elevated gas temperatures from the early trials on large coal fired boilers to specially made burner rigs and the Spey gas turbine are discussed. A patent for the ceramic temperature probe was filed and approved. Finally, a non-intrusive infra-red thermal pyrometry was installed on two of National Power's CCGT power stations. The report includes technical aspects on emissivity, radiation, risks, obstacles encountered, and the methodology used to install the pyrometry. Using the data collated from Deeside Power Station, where two pyrometers are currently installed, the results obtained from the engine simulation are validated. Once the model was validated and the data correlated with the actual data obtained, it can be concluded that the deployment of pyrometry can control the diagnostics and operational behaviour of the CCGT plant. The efficiency of the gas turbine was shown to increase by about 0.4% and the corresponding increase in power was 1.3%, which would make a substantial savings in the operating and maintenance costs to National Power. This was estimated to be in access of £25,000,000/annum.

No description available.